Cytokine-driven PANoptosis of alveolar macrophages mediated by STAT1 underlies acute lung injury in hypervirulent <i>Klebsiella pneumoniae</i> infection

ABSTRACT Understanding the fundamental mechanisms that govern innate immune and inflammatory responses during Klebsiella pneumoniae ( Kp ) infection is critical for developing effective therapeutic strategies against this public health threat. We found that hypervirulent Kp (hv Kp ) infection led to a significant depletion of alveolar macrophages (AMs) in mice. Single-cell RNA sequencing (scRNA-Seq) analyses suggested that this loss was associated with the activation of cell death signaling pathways. Further investigation confirmed that hv Kp infection simultaneously activated key executioners of pyroptosis, apoptosis, and necroptosis, indicating the induction of PANoptosis, a synergistic cell death process. Cell-cell communication analysis revealed significant enhancement of pro-inflammatory signaling pathways, including TNF and IFN-II, in infected lungs. Mechanistically, cytokines produced during infection, particularly IFN-γ in combination with others, synergistically induced PANoptosis in macrophages. The key transcription factor STAT1 was significantly activated upon infection. STAT1-deficient mice exhibited markedly reduced AM loss, bacterial burdens, tissue damage, and mortality following hv Kp challenge, alongside impaired activation of key PANoptotic effectors. Furthermore, STAT1 deficiency indirectly regulated inflammatory death in AMs by impairing IFN-γ production in immune cells like NK cells. In summary, this study reveals that hv Kp infection triggers STAT1-dependent PANoptosis in AMs, leading to immune cell death, organ failure, and high mortality, providing new insights into the pathogenesis of severe Kp infections. IMPORTANCE Klebsiella pneumoniae , particularly hypervirulent strains (hv Kp ), poses a critical public health threat due to its capacity to cause severe, rapidly progressing infections such as pneumonia and sepsis, often leading to acute lung injury (ALI) and high mortality. Despite the recognized role of excessive inflammation and cytokine storms in hv Kp pathogenesis, the precise mechanisms linking immune hyperactivation to fatal tissue damage remain poorly defined. This study reveals that hv Kp infection triggers a coordinated form of inflammatory cell death, PANoptosis, in AMs, the frontline immune defenders in the lungs. We identify the transcription factor STAT1 as a central regulator of this process, driven by a synergistic cytokine milieu, especially involving IFN-γ. Our findings establish a direct mechanistic pathway from hv Kp -induced cytokine release to STAT1-mediated PANoptosis, macrophage depletion, and subsequent lung failure. This work not only advances the understanding of hv Kp virulence but also highlights host signaling pathways and specific cytokines as potential therapeutic targets to modulate immunopathology and improve outcomes in severe Klebsiella infections.